This invention relates primarily to vehicle testing equipment in which the vehicle wheels are supported upon, and rotate with, rollers in a test bed. The concepts are primarily applicable to situations in which the roller drives the wheel, such as brake analyzers or other motoring dynamometers.
The present invention particularly concerns itself with improving roller construction for use in relatively low speed testing equipment. It could, of course, be used also in higher speed equipment, but the maximum feasible speed tends to be controlled by noise problems.
Lower speed test bed rollers normally require high torque, which means that high traction is necessary to operate properly. In developing high traction, a common prior art expedient is to use ribs on the roller which extend at right angles to the direction of motion of the tire periphery which engages the roller. The ribs press into the tire causing a series of distortions in the tire periphery, i.e., causing localized indentations in the tire where the ribs engage, and bulges in the tire between successive ribs. This tends to "lock" the tire and roller together in their rotational movements, resulting in low slippage. In Europe, where low speed dynamometers are used extensively, other types of roller structures used to develop high traction have been porous concrete roller surfaces and expanded metal roller surfaces. Both of these expedients, particularly the latter, tend to abrade the tire surface.
My invention uses axially-extending ribs on the roller, but the roller is so constructed that several valuable advantages are obtained:
A. The cost of constructing the rollers is minimized, particularly for a manufacturer having adequate press-working, or stamping equipment;
B. The roller is particularly "easy" on the tire surface, and also has higher traction than most others;
C. When the tire-engaging ribs wear down, this construction permits convenient and inexpensive replacement of the ribs without altering the basic construction of the roller; and
D. Water is quickly drained from the roller-engaging tire surface due to the "open" construction of the roller.